1. Field of the Invention
The present invention relates to a method for controlling a driving circuit of a light-emitting device and related electronic device and light source system, and more particularly, to a method and related electronic device and light source system for generating a light source of specific luminance and chrominance by controlling turn-off time of power.
2. Description of the Prior Art
In daily life, people need to change luminance and chrominance of light depending on different environment. For example, soft light is needed when dining, whereas bright but not harsh light is needed when reading. Therefore, the prior art provides different operations for users to control light conveniently, such that users can change luminance and chrominance of light emitted by a light-emitting device, e.g. a light emitting diode, via a switch. Since luminance and chrominance of light emitted by the light-emitting device are related to amplitude or duty cycle of an input power, the switch can be designed to vary amplitude or duty cycle of the input power, so as to realize the purpose of changing luminance and chrominance. In addition, changing duty cycle is usually realized by angular modulation, such as pulse width modulation (PWM).
Please refer to FIG. 1. FIG. 1. is a schematic diagram of a light source system 10 in the prior art. The light source system 10 comprises a light-emitting device 100, a switch device 102 and a pulse width modulation device 104. The light-emitting device 100 can be a light emitting diode, and is utilized for generating a light source according to received power. The switch device 102 can be an on-off switch, and is utilized for receiving control signals triggered by a user and transmitting the control signals to the pulse width modulation device 104. The pulse width modulation device 104 is utilized for transforming an input signal VIN into an output signal VOUT according to signals provided by the switch device 102, and transmitting the output signal VOUT to the light-emitting device 100 to emit light. When the user needs to control luminance and chrominance emitted by the light-emitting device 100, the user can adjust pulse width of the output signal VOUT, namely T1, via the switch device 102, to make the light-emitting device 100 to emit required light.
Via the pulse width modulation device 104, the user can adjust luminance and chrominance of the light source system 10. However, a circuitry of the pulse width modulation device 104 is more complicated, resulting in high production cost which limits its applications.